Although nearly 15 percent of adults experience chronic primary insomnia, few have sought or have access to effective behavioral treatments for this condition. The purpose of this project is to design, develop, and evaluate a computerized self-help intervention that provides a comprehensive behavioral treatment of insomnia. A Phase I prototype of the Insomnia Assessment and Treatment Program (IATP) was developed which assessed sleep and wake states using an active sleep sampling procedures and then implemented a stimulus control and sleep restriction intervention. The resulting prototype was evaluated with 86 subjects, comparing the IATP to a comparison group provided with monitoring and educational treatment components only. Despite the active components of the comparison group, the IATP condition produced superior improvement on most of the sleep parameters evaluated during the trial. For Phase II, the program will be redesigned and redeveloped on a specific purpose platform. The program will be evaluated in a randomized controlled trial of 200 subjects with chronic primary insomnia, comparing the IATP treatment program to a self-help behavioral treatment book for insomnia and the IATP device for monitoring purposes only. Subjects will be evaluated at baseline and at weeks 7, 14, and 28 on sleep diary and self-report data of sleep quality, efficiency, and impairment. Home-based, multi-night polysomnography also will be performed on a subset of the sample at baseline and at 14 weeks. The results of this project could produce an empirically validated behavioral treatment for insomnia, which is easily accessed by the millions of people suffering from chronic primary insomnia.